1. Field of the Invention
This invention relates to a composition water soluble polymers and surfactants and more particularly it relates to a composition comprising cellulose ethers, guar, or derivatives thereof and sorbitan esters, such compositions having improved dispersibility in water.
2. Description of the Prior Art
Water soluble polymers are used widely to prepare a variety of aqueous solutions among which cellulose ethers (CES), or guar, or derivatives thereof find wide application as thickening and suspending agents.
In the preparation process of aqueous systems, incorporation of water soluble cellulose ethers or cellulose ether derivatives into the composition often present difficulties because of the tendency for lump formation when the polymers are added. In fact, in contact with water, local gel formation can occur around particles of undissolved cellulose ether, which prevent the hydration of the polymer matrix. The disaggregation/dissolution of the agglomerates or lumps when formed is very time consuming. Consequently, there is a need for method of incorporating CEs and CE derivatives which lead to improved polymer dispersion and rapid viscosity development and which allow convenient handling of the polymer.
To overcome the lumping problems, various types of approaches have been attempted. These include coating the particles with glyoxal, processing with larger particles, granulated CEs, blending the CEs with fatty acid salts, surfactants and/or silica, suspending the CEs in non solvent medium (Fluid Polymer Suspensions: FPSs). However, these treatments exhibit use limitations in some applications. For instance, glyoxal treated CEs show poor dispersibility in an alkaline environment (such as drilling muds); larger particles avoid the lumping problems but they require longer dissolving time; liquid compositions have the disadvantage of relatively low solids content resulting in high cost and blend of CEs and other ingredients present the disadvantage of reduced active polymer content; etc.
U.S. Pat. No. 5,391,359 describes water dispersible thickeners comprising hydrophilic polymers coated with particulate fatty acids or the salts thereof. The composition is a blend of CE (CMC), starches and gums with finely divided particulate dispersant (more preferably from 2% to 20%) such as fatty acid or fatty acid salts (Al, Ca, Mg & Na stereate). Hydrophobic fumed silica was used for comparative purposes.
E.P. Patent 0 658 596 discloses a fast hydration bio-polymers composition that contains a composition of bio-polymers and surfactants at ratios varying from 0.1% to 1.5% total wt. The composition is said to be non-dusting and to have fast hydration time. The composition is said to be useful as suspending agent in industrial formulations, cosmetics, food and pharmaceuticals.
U.S. Pat. No. 5,003,060 teaches preparation of solid, free flowing and nondusting granules of polysaccharides of microbial origin, e.g. xanthan gum, by granulating the powder in a fluidized bed. Such granules may contain at least one wetting agent (0.5-10% w/w, including polyethoxylated sorbitan esters) or combination thereof and have a particle size varying from 0.5 mm to 2.0 mm and apparent density below 0.7. The granules are said to contain only small amount of anti-agglomerating additive and disperse instantaneously in water with rapid dissolution and are used as thickeners e.g. for drilling in petroleum recovery.
U.S. Pat. No. 4,720,303 describes the manufacture of thickening agent, comprising a mixture of a CE and solid acid, suitable for thickening carpet backing formulations, paints and drilling muds. The thickening agent can be used to thicken in acid, neutral and/or alkaline media. It is also disclosed that the thickening agent can easily be dispersed without lump formation.
U.S. Pat. No. 4,735,659 discloses a process for preparing water dispersible compositions containing hydrophobic silica to prevent agglomeration of initial wetting of CEs, gums, starches, vinyl polymers, acrylic polymers and bio-polysaccharides. It is disclosed that water soluble high Mw polymer is contacted with hydrophobic fumed silica in such manner that the individual particles are coated with hydrophobic fumed silica. The resulting composition is disclosed to readily dissolve in water producing a translucent solution; if clear aqueous solution is desired, a surfactant can optionally be added. A composition of CMC and CMHEC mixed with 2% hydrophobic fumed silica were used for comparative purposes.
U.S. Pat. No. 4,654,086 discloses composition and preparation of dispersible xanthan gum obtained by treatment with surfactant which is a food approved wetting agent e.g. lecithin, sorbitan esters, etc. The xanthan/surfactant blends w/w ratio is disclosed to vary from 95/5 to 80/20. Liquid surfactants can be added directly to xanthan gum powder to uniformly coat the particles.
U.S. Pat. No. 4,218,262 describes a nonclumping, delayed action viscosity increasing agent comprising core particles of xanthan gum and an encapsulating coating of a fat derivative and a surfactant wherein the coating has a hydrophilic/lipophilic balance (HLB) of from 3.5 to 10. The fat derivative is selected from the group consisting of fatty acids and mono and diglycerides of fatty acids. The surfactant is selected from the group consisting of alkali metal salts of fatty acids. Methods of forming the encapsulated particles are also disclosed.
U.S. Pat. No. 3,960,584 relates to a composition of matter consisting of finely divided, high Mw, water soluble polymeric material in intimate mixture with other components (from 1 to 4) and a process for the preparation thereof. The water soluble polymeric material is selected from the group consisting of acrylics, natural gums, CEs and CE derivatives. The other components are disclosed to be polyglycols, and anionic and non-ionic surfactants. The invention composition is disclosed to disperse and dissolve quickly in aqueous media without skinning and agglomeration. The polymeric material is disclosed to be useful as a flocculent and thickener in many industrial processes.
None of the aforementioned references discloses a composition comprising cellulose ethers, or guar, or derivative thereof and sorbitan esters.